PeachParts Mercedes-Benz Forum - View Single Post - A/C System

tinypanzer · #2 09-01-2009, 12:04 AM

Okay, where to start. First off, I'm no A/C expert, but I can give some minor advice.

If you're not getting voltage to the A/C clutch with the A/C turned on, then indeed there may be an electrical issue. That issue could reside in a relay or in the climate control unit. There may also be a low-side pressure sensor that is preventing the clutch from coming on because the refrigerant charge is too low.

You really need to get a hold of a manifold set. Hook up the manifold to the low side (if you don't know about high and low side then stop now and call a pro). Start the engine. You need to have at least about 35-45 psi on the low side for the system to be happy. Too far below that and the compressor will never turn on. If you have adequate pressure on the low side, then the problem could be the pressure switch. Bypassing this switch (temporarily!!) will allow you to see if the compressor will kick in. Don't bypass this switch unless you have adequate low side pressure. If you have inadequate low-side pressure, it may be as simple as adding some R-12. If your charge is completely gone, then air has probably infiltrated the system and a complete leak check, evacuation, new receiver/dryer, seals, etc. are in order.

Report back your findings. Hopefully by then somebody more knowledgeable about MB A/C systems will have joined the thread at that point......

You really should get a hold of a shop manual for your A/C system, or have somebody with WIS print out the troubleshooting steps and the wiring diagram.